Although a number of shelters, tents and insulation systems are known or have been suggested in the art, they all have or would have disadvantages. Japanese Patent No. 2004-132006 (Kawahara), for example, discloses a heat-insulating layer for a tent. An air layer D is formed between the tent 3 and a canopy sheet 5. As shown in FIG. 4 of Kawahara, cylindrical members 4 are attached to the exterior cover 5 by staple-shaped elements 8. The Kawahara tent requires a device f for forcing air through a duct d, which would waste energy, and the Kawahara tent is unduly complicated and unreliable, and it would be difficult to transport and set up, especially in remote, harsh environments.
U.S. Patent Application Publication No. 2009/0188539 (Hollinger) refers to the use of inert gas or low pressure within hollow or airtight tubes 901, 911 (FIGS. 9A, 9B) to provide insulation within a multi-layer tent. The Hollinger tent would require a source of inert gas, which would be impracticable, or inflation/deflation of the tubes, and the tubes would be subject to puncturing and damage, or additional construction expense would be required to make them sufficiently rugged. The Hollinger tent is unduly complicated and unreliable, and would be difficult to transport and set up, especially in remote, harsh environments.
Japanese Patent No. 2006-265849 to Shimizu discloses a fabric shelter (FIG. 14), and other shelters known in the art are shown in U.S. Pat. No. 4,102,352 (Kirkham), U.S. Pat. No. 4,607,655 (Wagner et al.), and U.S. Pat. No. 7,178,483 (Wu).